The present invention relates to an image formation apparatus.
With the progress in electronic video equipment, image formation has been performed using recording heads of ink jet or thermal transfer types. Particularly, in order to attain high-speed printing, the recording heads have been increased in size or have been formed from multiple heads.
However, with the ink jet-based image formation, there are variations in the amount or direction of ink ejected from nozzles of a recording head. The variations may apparently form irregularities in image density such as lines. The image irregularities remarkably appear in large recording heads and multi-head systems. Thus, irregularities in the line form are produced with a period corresponding to the width of the recording head, which constitutes a factor degrading considerably print quality. The variations also vary with time in the case of recording over a long period of time.
Japanese Patent No. 2748321 discloses a method of correcting such irregularities in density. In the image formation in which image data is converted into binarized image data and on-off control of each nozzle is performed in accordance with the binarized image data, this method uses an irregularity correction table provided ahead of the binarization unit, thereby correcting the multivalued image data. By correcting variations in the amount or direction of ejected ink from nozzle to nozzle with such a method, irregularities in image density can be corrected.
However, in order to make irregularity correction on input multivalued image data prior to the binarization, it is required to take into consideration how the input multivalued image data is converted into binarized image data. That is, the correction of irregularities in image density depends on the method of binarization. In addition, the expansion of density caused by binarization may result in a failure to correct irregularities in image density accurately. Moreover, the provision of the binarization unit on the outside of the image formation apparatus makes it impossible to make correction of irregularities in image density on the inside of the image formation apparatus, resulting in a failure in automated correction.
It is therefore an object of the present invention to provide an image formation apparatus which makes density irregularity correction for image data already subjected to binarization, thereby permitting precise density irregularity correction to be made automatically within the apparatus independently of binarization processing.
To attain the object, an image formation apparatus of the present invention comprises: a recording head having a plurality of recording elements for recording an image on a recording medium; binarized image data storage unit for storing binarized image data for on-off control of the recording elements of the recording head; correction data storage unit for storing density irregularity correction data for correcting irregularities in density which occur when the recording elements of the recording head are respectively driven to form the image, the density irregularity correction data being stored in correspondence with each of the recording elements; and density irregularity correction unit for, prior to the image formation, correcting the binarized image data stored in the binarized image data storage unit on the basis of the density irregularity correction data stored in the correction data storage unit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.